Telescoping expansion joint
“How can we implement an expansion joint for tubular geometries?”
Expansion joints are very useful devices. However, how can we create affordable versions to implement on tubular geometries such as in pipes? First of all, let’s look at the problem at hand. Thermal expansion causes a material to change it’s size depending upon the surrounding temperature, and as such there needs to be “breath gaps” to ensure that a structure will not collapse. However, using something like a plaster or a soft filling will not be strong enough to sustain the expected pressures on a pipe, and having loose material might cause a leakage into the fluid flow. Therefore, we will have to think of an adjustable solid part. Well, how about we take some design inspiration from one of humanity’s greatest achievements, the telescope. Part of what makes telescopes the machines they are is the fact that they have a telescoping build, which means that solid parts are made so that they can slide past each other. Now, how about we take this mechanism and apply it to our thermal expansion joints?
Well, what we could do is have two concentric expansion tubes, one with a larger tube and the other with a smaller one. The smaller diameter tube will connect to the two joints of the mechanism, and will expand and contract upon need. The larger diameter tube will act as a fixed support in order to center the smaller diameter tube, and as such have a smaller diameter. You can analogize the larger diameter tubes as being like the “braces” of the smaller diameter tube. O-rings are often used to seal these parts to ensure that all operations are smooth. This layout is known as a telescoping expansion joint. Telescoping expansion joints are very useful due to their simple yet effective design, and the fact that they can be curated for tubular geometries.